From the results shown over the course of 10 days,we can tell that the higher the amount of preservatives,the lower the amount of mould grown.
As the bread pieces were given equal amounts of warmth,moisture and air.(Conditions required for mould growth),the area of mould growth would have been affected only by the amount of preservatives.
However,the higher amount of preservatives in the bread also mean the higher the amount of chemicals a person consumes from the bread.And as the preservatives that we used were more for experimental purposes than consumption,we cannot precisely determine whether the "poison" in the bread is really the preservative or the mould.
The best way to increase shelf life would be to add natural preservatives.